Switchboard-cord.



PATENTED MAY 9, 1905.

iNo. 789,652.

W. J. BURTON.

SWITCHBUARD CORD.

LPPLIGATION FILED rms. 9. 1904.

def/265%@ `a permanent curve therein.

atented May 9, 1905.

`UNITED STATES PATENT OEEIcE.

WILLIAM J. BURTON, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TO JUANI'IA M. BURLINGHAM, OF CHICAGO, ILLINOIS.

SWITCHBOARD-GORD.

SPECIFICATION forming part of Letters Patent No. 789,652, dated May 9,1905.

Application filed February 9, 19011. Serial No. 192,822.

T0 all wwm, zit muy concern:

Be it known that I, WILLIAM J. BURTON, a citizen of the United States,residing' at Chicago, county of Cook, State of Illinois, have inventedacertain new and useful Improvement in Switchboard-Cords; and I declarethe following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itpertains to Inake and use the same, reference being had to theaccompanying drawings, which form a part of this specification.

My invention relates in general to electrical connectors, and moreparticularly to flexible cords-such, for instance, as are used forconnecting subscribers at a telephone-switchboard.

It is essential that flexible electrical connectors which are subjectedto frequentuse in completing circuits should possess the requisiteelectrical conductivity and at the same time be sufficiently strong andresilient structurally to stand constant bending without breaking' ordestroying the conductivity. Owing to the lack of resiliency andstrength of copper, considerable dificulty has been experiencedheretofore in constructing iiexible connectors-such, for instance, asswitchboard-cords-which will stand constant usage without wearing out orshort-circuiting in a comparatively short while, especially when thediameter of the connector is necessarily of limited size. The wear andtear on switchboard-cords is most severe throughout the portion thereofadjacent to the plug', owing to the plug being forced into theswitchboardsockets by pressure applied to the end thereof, which bendsthe cord and soon produces Each subsequent insertion of theY plugrenders such curve Inore acute, eventually either breaking the conductoror destroying the insulation.

rIhe primary object of Iny invention is to provide a switchboard-cordwhich will possess sufficient resiliency to immediately return to itsnormal position with respect to the plug after each insertion of thelatter in a socket, so that the cord will not become permanently bent,thereby yprolonging the life of the cord by obviating the breaking orshort-circuiting of the conductors therein.

A further object of my invention is to provide a flexible electricalconnector which will be simple in construction, inexpensive inmanufacture, and durable in use.

The embodiment of my invention herein disclosed consists, generallydescribed, in a switchboard -cord comprising one or morespirally-disposed conductors united at its opposite ends to plugs andresilient reinforcements located within the convolutions of theconductors and extending from within the plugs throughout the portionsof the cord on which pressure is applied by the operator inserting theplugs in the switchboard-sockets.

My invention will be more fully described hereinafter with reference tothe accompanying drawings, in which the same isillustrated as embodiedin a convenient and practical form, and in which- Figure l illustrates aplan view, with parts broken away, of a portion of a cord embodying myinvention; and Fig. Q, an enlarged detail view of the resilientreinforcing-rod.

The same reference characters are usedto designate the same parts of thetwo figures of the drawings.

I have illustrated my improvement as applied to a switchboard-cordconstructed as d escribed and claimed in the joint application filed bymyself and Charles L. Burlinghani on February 16, l1903, Serial No.143,509. The joint invention covered by said application consists in oneor moreinsulated spirallywound conductors, each conductor consisting ina wire A of a metal possessing strength and resiliency--such, forinstance, as brass, aluminium, orsteel-around which aline copper wire Bis wound to impart to the conductor the necessary electricalconductivity. An insulating-covering C is wound around each conductor,which may conveniently consist in silk, around which an outerinsulatingcovering D is placed to retain the silk insulation in positionaround each conductor, such outer covering preferably consisting' inbraided thread.

The conductors are wound together in the vIO form of a spiral, which isincased in an outer covering E of braided cotton thread and a secondcovering F, composed of braided linen thread. Then the conductor is tobe used as a switchboard-eord, its opposite ends are secured withinplugs, such as indicated at Gr, consisting in a casing made ofinsulating' material, within which are the usual conductors G and G2,insulated from each other, as indicated at g, to the latter of which oneof the conductors of the cord is united by a set-screw, while the otherconductor of the cord is bent into close contact with the conductor G ofthe plug'.

A number of conductors may be wound in a spiral without increasing' thediameter of the cord, and by so arranging the conductors the cord isrendered thoroughly iiexible. As each conductor consists in an interiorwire possessing' structural strength and resiliency and of a surroundingmetal comprising' high electrical conductivity, a conductor resultswhich possesses the requisite conductivity and at the same time isstructurally strong. 1n order, however, that the repeated pressureapplied to the portions of the cord adjacent to the plugs incident tothe insertion and removal of the plugs from the switchboard-sockets maynot permanently bend the cord, and thereby either break the conductorsor destroy their insulation, I have found it expedient to insert withinthe convolutions of the conductors a resilient rod H, which extends froma point within the plug G throughout the adjacent portion of the cord.Such rod H must possess suflicient resiliency to at once spring backinto its normal position upon pressure being removed from the cord. Suchrod preferably consists in a spirally-wound wire L, the convolutions ofwhich are in close contact with each other, as clearly shown in Fig. 2.Around the resilient rod /t is placed an insulatingcovering to obviateany danger of such rod producing a short circuit through contact withthe conductors should the insulation around the same become worn off.

By providing the resilient rod within the cord the plug' may be insertedby the operator applying' pressure to the end thereof without danger ofthe cord becoming' permanently bent, as the resilient rod at oncesprings back into its normal position upon the plug' being' inserted.The breaking' of the conductors or the wearing out of the insulationaround the same is therefore prevented and the longevity of the cordgreatly increased.

W'hile I have described more or less precisely the details ofconstruction, I do not wish to be understood as limiting' myselfthereto, as I contemplate changes in form, the proportion of parts, andthe substitution of equivalents as circumstances may suggest or renderexpedient without departing from the spiritof my invention.

Having now fully described my invention, what I claim as new, and desireto secure by Letters Patent, is

l. A flexible electrical conductor wound in parallel convolutions to'form a single continuousspiral, said conductor reinforced by aresilient rod located within said spiral at a predetermined locality.

2. The combination with a fiexible electric conductor comprising aplurality of insulated conductors wound in parallel convolutions to forma single continuous spiral, of a resilient rod located within saidspiral.

3. In a telephone-switchboard cord, the combination with aconnecting-plug', of a liexible conductor composed of a strong resilientwire around which is wound a goed conducting material, said conductorbeing wound in parallel convolutions, and a resilient rod surrounded bysaid eonvolutions and extending' a predetermined distance from a pointwithin said plug.

4C. The combination with a flexible electrical connector comprising aplurality of insulated conductors wound in parallel convolutions to forma single continuous spiral, each conductor composed of a strong'resilient wire surrounded by a good conducting material, of a resilientrod located within said spiral.

In testimony whereof I sign this specification in the presence of twowitnesses.

IVILLIAM J. BURTON.

INitnesses:

Guo. L. WILKINSON, C CUNNINGHAM.

